Beat McEnroe at US Open

I can confirm that you can, in fact, earn these trophies in the first season of a career. I went through an entire 10 year career and never faced Borg at the French Open, so I kept restarting career mode and eventually I was able to get him in the same quarter of the draw with no other professionals between him and the quarter-final, fortunately he progressed through and I beat him. You still need to get lucky and I would suggest that if the player you need is not at the very least in the same half/side of the draw as you in the first season, it's a non-starter and you should either skip or restart.